1. Field of the Invention
The present invention relates to a paper-making machine, and, more particularly, to a paper-making machine including a felt.
2. Description of the Related Art.
Paper-making machines may include continuous belts such as so-called "felts" to conduct the paper web throughout the paper-making machine. These felts, also sometimes called "canvases," are carried by rotating rolls. A plurality of felts may be provided which successively carry the fiber web from one end of the paper-making machine to the other end. Such felts can generally be viewed as conveying, dewatering and drying felts. A drying felt traveling in a dryer section of a paper-making machine can contract or shrink due to the heat that the felt is exposed to within the dryer section, and can expand upon absorption of water from the paper web. Consequently, such drying felts may need to be stretched during operation.
It is known to stretch a felt carried by a roll by coupling each end of the roll to a separate gear box via cross shaft systems. The gear boxes, driven by electric motors, move the cross shafts, which, in turn, press the roll against the felt, thereby stretching the felt. The cross shafts may be attached to each end of a concentric axle of the roll. To stretch the felt, the roll can either be pulled toward or pushed away from the gear boxes by the cross shafts. A problem is that the gear boxes must be synchronized to exert substantially the same force to either end of the roll so that one end of the felt is not stretched more than the other end, and so that the roll does not become misaligned. This is particularly problematic in that the gear boxes must be synchronized while being separated by the approximately, e.g., 10 meter length of the roll. Electronic control may be needed to achieve this long distance synchronization. Another problem is that gear boxes and electronic controls are relatively expensive.
It is also known to stretch a felt carried by a roll by using an electric motor to tension a chain attached to one end of the roll axle, thereby pulling the roll into the felt. Another such device is attached to the other end of the roll axle. A problem is that, like the gear boxes, a substantially equal force must be applied to each end of the roll. Another problem is that such a device is not durable because it vibrates excessively in operation, shakes itself loose, and batters its components against themselves and other objects.